Cruise control operation may be used for autonomously regulating a vehicle's speed near a target speed. One method that can reduce fuel consumption while operating cruise control is a Pulse and Glide (PG) speed-control strategy, where time-dependent periodic control of the vehicle's speed is implemented. During the pulse portion of the PG speed-control strategy, the vehicle is accelerated to a threshold speed above the target speed. Subsequently, the engine is shut off during the glide portion of the PG speed-control strategy, until the vehicle decelerates to a threshold speed below the target speed. By repeating this PG speed-control strategy in a periodic manner, the vehicle can be driven with an average speed equivalent to a desired target speed, but with higher fuel economy, by taking advantage of lower pumping losses during the pulse phase, during which the engine is operated close to or at wide open throttle.
The inventors herein have recognized potential issues with the PG speed-control strategy. Namely, because the PG speed-control strategy requires alternating periods of acceleration (e.g., pulsing) and deceleration (e.g., gliding), it can also cause periodic pitching of the vehicle (e.g., nose-up or squatting during pulsing, nose-down or diving while gliding) that can cause ride discomfort, especially for long drives.
One approach that addresses the aforementioned issues is a method that coordinates or synchronizes control of the vehicle suspension systems with PG speed-control strategy. In one example, a vehicle's active suspension can increase stiffness at the vehicle's rear wheels during acceleration, and can increase stiffness at the vehicle's front wheels during deceleration. In this way, the overall ride comfort can be increased, while still enabling fuel economy gains.
In another example, during pulsing and gliding, the method adjusts the vehicle suspension to reduce variation in vehicle height (e.g., front vehicle height), thereby reducing ride discomfort, while maintaining fuel economy. In another example, the method can pre-adjust the vehicle suspension in anticipation of the pulsing and gliding disturbances, based on the PG speed-control parameters, in order to further reduce ride discomfort while maintaining fuel economy.
The above advantages as well as other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.